Office of Steam Forum for Model & Toy Steam Gas & Hot Air Engines

Actually, without any train tonnage coupled on behind them, those engines are graced with full adhesion due to their own weight, without any drag from behind that they have to try and get started moving. Not saying that they couldn't spin their wheels trying for a fast start, but just that it is vastly less likely to happen when only pulling their own weight. In a situation like that the advantage would likely go to the smaller engines mostly because they almost certainly have smaller diameter drivers, and thus are operating in what is effectively a lower gear!

For the exact same reason that the little engines are most likely to win a short sprint, it is the larger engines with greater wheel diameters that would be certain to win a longer race with higher "geared" top speed potential!!!